Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A recording tape cartridge capable of keeping position error signals
during running of a recording tape small. A recording tape cartridge is
provided with a reel hub, a magnetic tape that is wound round the reel
hub, and a lower flange and upper flange that are disposed to oppose one
another at each of the both axial direction ends of the reel hub. In a
state in which the magnetic tape is completely wound on the reel hub, the
magnetic tape is offset toward the upper flange. A space of an edge
clearance between a lower end of an outermost periphery portion of the
magnetic tape and the lower flange is at least 0.18 mm and at most 0.46
mm. A rate of widening of a facing distance between the lower flange and
the upper flange increases toward the outer periphery side.

Claims:

1. A recording tape cartridge comprising: a hub; a recording tape that is
wound around the hub; and a pair of flanges, the respective flanges being
provided to face one another at either end in an axial direction of the
hub, a distance in the axial direction between an outermost peripheral
portion of the recording tape and the flange in a state in which the
recording tape is completely wound around the hub being from 0.18 mm to
0.46 mm, a facing distance between the flanges being wider at an outer
peripheral side than at an inner peripheral side of the flanges, and a
rate of widening of the facing distance between the flanges increasing
toward the outer peripheral side.

2. The recording tape cartridge of claim 1, further comprising a driven
gear that is configured at the hub or at one of the pair of flanges such
that a position of the hub in the axial direction with respect to a drive
device is set, at mesh-faces that are inclined with respect to the axial
direction, by the driven gear being meshed with a driving gear at the
drive device so as to be capable of transmitting rotation.

3. The recording tape cartridge of claim 1, wherein a surface roughness
of a face at a recording tape side of at least one of the pair of flanges
is from 0.5 μm to 2 μm as a center line average roughness.

4. The recording tape cartridge of claim 2, wherein a surface roughness
of a face at a recording tape side of at least one of the pair of flanges
is from 0.5 μm to 2 μm as a center line average roughness.

7. The recording tape cartridge of claim 1, wherein: the hub is formed in
the shape of a circular tube with a bottom, of which one end side in the
axial direction is opened and the other end side is closed; and of the
pair of flanges, a flange that is disposed at the one end side of the hub
comprises a material with an elastic modulus equal to or greater than an
elastic modulus of a material forming the hub, and a flange that is
disposed at the other end side of the hub is integrated with another end
portion of the hub.

8. The recording tape cartridge of claim 2, wherein: the hub is formed in
the shape of a circular tube with a bottom, of which one end side in the
axial direction is opened and the other end side is closed; and of the
pair of flanges, a flange that is disposed at the one end side of the hub
comprises a material with an elastic modulus equal to or greater than an
elastic modulus of a material forming the hub, and a flange that is
disposed at the other end side of the hub is integrated with another end
portion of the hub.

9. The recording tape cartridge of claim 3, wherein: the hub is formed in
the shape of a circular tube with a bottom, of which one end side in the
axial direction is opened and the other end side is closed; and of the
pair of flanges, a flange that is disposed at the one end side of the hub
comprises a material with an elastic modulus equal to or greater than an
elastic modulus of a material forming the hub, and a flange that is
disposed at the other end side of the hub is integrated with another end
portion of the hub.

10. The recording tape cartridge of claim 5, wherein: the hub is formed
in the shape of a circular tube with a bottom, of which one end side in
the axial direction is opened and the other end side is closed; and of
the pair of flanges, a flange that is disposed at the one end side of the
hub comprises a material with an elastic modulus equal to or greater than
an elastic modulus of a material forming the hub, and a flange that is
disposed at the other end side of the hub is integrated with another end
portion of the hub.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority under 35 USC 119 from Japanese
Patent Application No. 2011-120683 filed May 30, 2011, the disclosure of
which is incorporated by reference herein.

BACKGROUND

[0002] 1. Field of the Invention

[0003] The present invention relates to a recording tape cartridge in
which a recording tape is used as a recording medium.

[0004] 2. Related Art

[0005] A magnetic tape cartridge is known (for example, see Japanese
Patent Application Laid-Open (JP-A) No. 11-306714) in which a facing
distance H between a pair of upper and lower reel flanges is set to a
value for which an excess gap E is added to a tape width of a magnetic
tape. The excess gap E is not more than a width dimension of a buffer
region of the magnetic tape. Further, a magnetic tape cartridge is known
(for example, see JP-A No. 2005-302256) in which a difference between the
facing distance, between a reference flange and an opposing flange, and
the width dimension of a magnetic tape is prescribed. Further yet, a tape
cartridge is known (for example, see JP-A No. 2009-211743) in which a
surface of the flanges is a grained surface with a surface roughness Ra
of between 0.5 μm and 2.0 μm. Further still, a technology is known
(for example, see Japanese Patent No. 4,679,733) in which a distance
between brim portions of a reel is prescribed and a running magnetic tape
is reliably aligned with a guide roller at a drive. Thus, position error
signals (PES) are made smaller.

[0006] Position error signals are a measure of mispositioning in a width
direction of a recording tape with respect to a head of a drive device
during running of the recording tape. In regard to keeping position error
signals small, there is still room for improvement in the dimensions and
shapes of a pair of flanges.

SUMMARY

[0007] The present invention is to provide a recording tape cartridge
capable of keeping position error signals (PES) during running of a
recording tape small.

[0008] A recording tape cartridge according to a first aspect includes: a
hub; a recording tape that is wound around the hub; and a pair of
flanges, the respective flanges being provided to face one another at
either end in an axial direction of the hub, a distance in the axial
direction between an outermost peripheral portion of the recording tape
and the flange in a state in which the recording tape is completely wound
around the hub being from 0.18 mm to 0.46 mm, a facing distance between
the flanges being wider at an outer peripheral side than at an inner
peripheral side of the flanges, and a rate of widening of the facing
distance between the flanges increasing toward the outer peripheral side.

[0009] In the recording tape cartridge of the first aspect, in the state
in which the whole of the recording tape is wound round the hub, the
distance of a gap (hereinafter referred to as the edge clearance) formed
between (a lower end of/an upper end of) the outermost periphery portion
of the recording tape and the pair of flanges (a lower flange/an upper
flange) is in a range which is from 0.18 mm to 0.46 mm (more than or
equal to 0.18 mm, less than or equal to 0.46 mm). If the edge clearances
are formed at both hub axial direction sides, the sum of the distances of
the edge clearances is in a range which is from 0.18 mm to 0.46 mm (more
than or equal to 0.18 mm and less than or equal to 0.46 mm).

[0010] The present inventors have attained new knowledge that the smaller
the width of an edge clearance, the more position error signals (PES),
which are a measure of mispositioning in the width direction with respect
to a head of a drive device during running of a recording tape, are
suppressed. In the present recording tape cartridge, the rate of widening
of the facing distance of the pair of flanges increases further toward
the outer periphery side. Therefore, compared to a configuration in which
the rate of widening of a facing distance between a pair of flanges is
constant, the edge clearance is smaller at the inner periphery side. That
is, a range in which the edge clearance is small is expanded toward the
outer periphery side. Therefore, in the present recording tape cartridge,
in a configuration in which the edge clearance distance at the outermost
periphery side is prescribed to be within a predetermined range, position
error signals (PES) can be kept small at the inner periphery side, and an
average value of position error signals (PES) decreases.

[0011] Thus, in the recording tape cartridge according to the first
aspect, position error signals (PES) during running of the recording tape
can be kept small.

[0012] A recording tape cartridge according to a second aspect of the
invention is the recording tape cartridge according to the first aspect,
further including a driven gear that is configured at the hub or at one
of the pair of flanges such that a position of the hub in the axial
direction with respect to a drive device is set, at mesh-faces that are
inclined with respect to the axial direction, by the driven gear being
meshed with a driving gear at the drive device so as to be capable of
transmitting rotation.

[0013] In the recording tape cartridge of the second aspect, the hub is
rotated by rotating of the driving gear at the drive device side that is
meshed with the driven gear, and the magnetic tape is unwound from the
hub or wound onto the hub. An axial direction position reference of the
hub with respect to the drive device is the meshing faces of the driven
gear and the driving gear. Position error signals (PES) tend to become
large with such a structure. However, the position error signals (PES)
are kept small by the flanges with the shape described above.

[0014] A recording tape cartridge according to a third aspect of the
invention is the recording tape cartridge according to the first aspect
or the second aspect, in which a surface roughness of a face at a
recording tape side of at least one of the pair of flanges is from 0.5
μm to 2 μm (more than or equal to 0.5 μm, less than or equal to
2 μm) as a center line average roughness.

[0015] In the recording tape cartridge of the third aspect, because the
surface roughness of the flange(s) is set as described above, variations
in position in the width direction of the recording tape (the hub axis
direction) due to contact between the flange(s) and the recording tape
are less likely to occur, which contributes to the position error signals
(PES) being kept small.

[0016] A recording tape cartridge according to a fourth aspect of the
invention is the recording tape cartridge according to any one of the
first to third aspects, in which the hub and the flanges comprise
fiber-reinforced resin.

[0017] In the recording tape cartridge of the fourth aspect, because the
hub and the flanges are constituted of high-resilience fiber-reinforced
resin, deformations of the flanges (surface runouts) and the hub due to
tape winding pressure are suppressed, which contributes to the position
error signals (PES) being kept small.

[0018] A recording tape cartridge according to a fifth aspect of the
invention is the recording tape cartridge according to any one of the
first to third aspects, in which the hub is formed in the shape of a
circular tube with a bottom, of which one end side in the axial direction
is opened and the other end side is closed; and of the pair of flanges, a
flange that is disposed at the one end side of the hub comprises a
material with an elastic modulus equal to or greater than an elastic
modulus of a material forming the hub, and a flange that is disposed at
the other end side of the hub is integrated with another end portion of
the hub.

[0019] In the recording tape cartridge of the fifth aspect, the flange is
integrated with the bottom side of the hub, and the high-elasticity
flange is fixed with the opening end portion that is at the low-stiffness
side of the hub. Therefore, particularly deformations of the opening end
side of the hub and the flange at the opening end side (surface runouts)
due to tape winding pressure are suppressed, which contributes to the
position error signals (PES) being kept even smaller.

[0020] A recording tape cartridge according to the present invention as
described above has an excellent effect in that position error signals
(PES) during running of a recording tape can be kept small.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments of the invention will be described in detail with
reference to the following figures, wherein:

[0022]FIG. 1 is an exploded perspective diagram of a reel constituting a
recording tape cartridge in accordance with an exemplary embodiment of
the present invention.

[0023]FIG. 2 is a side view of the reel constituting the recording tape
cartridge in accordance with the exemplary embodiment of the present
invention.

[0024]FIG. 3 is a side view in which a principal portion of the reel
constituting the recording tape cartridge in accordance with the
exemplary embodiment of the present invention is shown magnified.

[0025]FIG. 4 is a perspective view in which a reel gear of the reel
constituting the recording tape cartridge in accordance with the
exemplary embodiment of the present invention is shown magnified.

[0026]FIG. 5 is a side view in which a portion of a magnetic tape
constituting the recording tape cartridge in accordance with the
exemplary embodiment of the present invention is shown magnified.

[0027]FIG. 6 is a graph illustrating a relationship between a facing
distance of a pair of flanges and position error signals.

[0028]FIG. 7 is a side sectional diagram of the recording tape cartridge
in accordance with the exemplary embodiment of the present invention when
not in use.

[0029]FIG. 8 is a side sectional diagram of the recording tape cartridge
in accordance with the exemplary embodiment of the present invention when
being used.

[0030]FIG. 9A is a perspective view, seen from above, showing the
recording tape cartridge according to the exemplary embodiment of the
present invention.

[0031]FIG. 9B is a perspective view, seen from below, showing the
recording tape cartridge according to the exemplary embodiment of the
present invention.

[0032] FIG. 10 is an exploded perspective view of reel lock structural
portions of the recording tape cartridge according to the exemplary
embodiment of the present invention.

DETAILED DESCRIPTION

[0033] A recording tape cartridge 10 according to an exemplary embodiment
of the present invention is described on the basis of FIG. 1 to FIG. 10.
First, general overall structure of the recording tape cartridge 10 is
described. Then, the structure of principal portions of a reel 11 round
which a magnetic tape T that serves as a recording tape is wound is
described. For convenience of description, a direction of loading of the
recording tape cartridge 10 into a drive apparatus in FIG. 1 is indicated
by arrow A, and serves as a forward direction (front side) of the
recording tape cartridge 10, and the direction indicated by arrow U is an
upward direction (upper side) of the recording tape cartridge 10.

[0034] --General Overall Structure of the Recording Tape Cartridge--

[0035] As shown in FIG. 7 to FIG. 10, the recording tape cartridge 10
according to this exemplary embodiment is provided with a case 12. The
case 12 is constituted by an upper case 14 and a lower case 16 being
joined together. Specifically, the upper case 14 is constituted with a
peripheral wall 14B in a substantial frame shape standing along an outer
edge of a ceiling (top) plate 14A with a substantially rectangular shape
in plan view, and the lower case 16 is constituted with a peripheral wall
16B standing along an outer edge of a floor (bottom) plate 16A with a
shape substantially corresponding with that of the ceiling plate 14A. The
opening end of the peripheral wall 14B and the opening end of the
peripheral wall 16B are matched up and, in this state, the case 12 is
formed into a substantial box shape by the upper case 14 and the lower
case 16 being joined together by ultrasonic welding, screw-fixing or the
like.

[0036] The ceiling plate 14A, the peripheral wall 14B, the floor plate 16A
and the peripheral wall 16B are each cut away at a corner portion of the
case 12 at the leading side in the direction of loading into the drive
device, and an opening 18 that is angled with respect the loading
direction is formed. A circular gear aperture 20 penetrating through the
floor plate 16A is formed at a substantially central portion of the floor
plate 16A, for exposing a reel gear 42 which is described below. An
annular rib 22 is provided at the floor plate 16A protruding to the
interior of the case 12 from an edge portion of the gear aperture 20. The
annular rib 22 is for positioning of the reel 11, which is described
below, and for dustproofing.

[0037] As shown in FIG. 7, the single reel 11 is rotatably accommodated in
the case 12. A magnetic tape T that serves as a recording tape is wound
onto the reel 11, and a leader block 30 that serves as a leader member is
attached to a distal end of the magnetic tape T. The leader block 30 is
accommodated and retained at the inner side of the opening 18 of the case
12 when the recording tape cartridge 10 is not in use. In this state, the
leader block 30 closes off the opening 18 and blocks ingressions of dust
and the like into the case 12.

[0038] When the magnetic tape T is to be drawn out inside a drive device,
the leader block 30 is taken out from the case 12 by a drawing member of
the drive device, and is guided to a take-up reel (not shown in the
drawings) of the drive device. A leader pin in a small rod shape or a
leader tape in a tape shape may be employed as the leader member instead
of the leader block. In such cases, for example, a door member is
provided at the case 12 for opening and closing the opening 18. Further,
the opening 18 may be formed along the peripheral wall 14B or 16B (only
the peripheral wall 14B or 16B being cut away).

[0039] As shown in FIG. 1 to FIG. 3, the reel 11 is provided with a reel
hub 32 that serves as a hub constituting an axial central portion of the
reel 11. The reel hub 32 is formed in the shape of a circular tube with a
bottom, including a tube portion 34 and a floor portion 36 that closes
off a lower portion of the tube portion 34. The magnetic tape T is wound
on an outer periphery face of the tube portion 34. A lower flange 38 that
projects to the radial direction outer side of the reel hub 32 is
provided at a vicinity of the floor portion 36 side end portion (lower
end portion) of the reel hub 32. An upper flange 40 that projects to the
radial direction outer side of the reel hub 32 is provided at the upper
end portion of the tube portion 34. The reel 11 is constituted such that
the magnetic tape T can be wound round the outer periphery face of the
tube portion 34 of the reel hub 32 between opposing faces of the lower
flange 38 and the upper flange 40. Dimensions and shapes of the lower
flange 38 and the upper flange 40 are described in more detail below.

[0040] The reel gear 42 is provided at an outer periphery vicinity of a
lower face (outer face) of the floor portion 36 of the reel hub 32. The
reel gear 42 is in an annular shape, is formed coaxially with the reel
11, and serves as a driven gear. The reel gear 42 is meshable with a
driving gear 102 that is provided at a distal end of a rotary shaft 100
of a drive device. When the reel gear 42 and the driving gear 102 are
meshed, the reel 11 is positioned in the axial direction with respect to
the drive device. Specifically, as shown in FIG. 4, meshing faces 42E of
the reel gear 42 that mesh with the driving gear 102 are inclined faces
that are inclined with respect to the axial direction, and form a meshing
structure with meshing faces 102E of the driving gear 102 (see FIG. 10)
such that the transmission of rotation is possible and the position in
the axial direction is set. An axial direction force for maintaining this
meshing acts on the meshing portions in the form of an urging force from
a compression coil spring 58 which is described below.

[0041] As shown in FIG. 1 and FIG. 10, an annular engaging gear 44 that is
formed coaxially with the reel 11 is provided at an outer periphery
vicinity of the upper face (inner face) of the floor portion 36 of the
reel hub 32. The engaging gear 44 is formed on an annular pedestal
portion 46 that protrudes a little from the inner face of the floor
portion 36. The engaging gear 44 is formed to be meshable with a braking
gear portion 55B of a brake member 55 which is described below.

[0042] A penetrating hole 50 is formed at an axial central portion of the
floor portion 36 of the reel hub 32. A clutch boss portion 52 is provided
standing from the upper face of the floor portion 36 along an edge
portion of the penetrating hole 50. The clutch boss portion 52 is
described below, together with a clutch member 60.

[0043] Principal portions of the reel 11 are formed by injection molding
of a fiber-reinforced resin, as described below. The reel includes an
annular reel plate 54 in the form of a metal plate that is fixed at the
inner side of the reel gear 42 at the lower face (surface) of the floor
portion 36 of the reel hub 32. The reel plate 54 is formed in an annular
shape of a magnetic material and is fixed to be coaxial with the floor
portion 36 of the reel hub 32. The annular reel plate 54 is for being
attracted and retained by a magnet 104 of the rotary shaft 100 of the
drive device.

[0044] The reel 11 described above is accommodated in the case 12 and
rests on (is placed on) the annular rib 22 of the case 12 when the case
12 is not in use. Specifically, an outer side region (a vicinity of an
inner edge of the lower flange 38) of a taper portion 43 of the floor
portion 36 that is continuous from the radial direction outer side of the
reel gear 42 abuts against an upper end face of the annular rib 22, and
an inner edge portion of the upper end of the annular rib 22 is formed as
a taper face 22A that matches up with the taper portion 43. Thus,
displacement in the radial direction is restricted.

[0045] In this state, the reel 11 is entirely (bodily) disposed inside the
case 12 and the reel gear 42 and reel plate 54 are exposed through the
gear aperture 20 (see FIG. 9B). That is, the reel gear 42 does not
protrude beyond the outer face (lower face) of the floor plate 16A but
faces outside the case 12 through the gear aperture 20. A through-hole
54A is formed at the axial center of the reel plate 54, and the
penetrating hole 50 faces the gear aperture 20 through the through-hole
54A. Thus, operations of the reel 11, that is, chucking (retention) and
rotary driving of the reel 11, may be performed from outside the case 12.

[0046] As shown in FIG. 7, FIG. 8 and FIG. 10, the recording tape
cartridge 10 is provided with the brake member 55, for blocking rotation
of the reel 11 when not in use. Principal portions structuring the brake
member 55 are a rotation restriction portion 55A and the braking gear
portion 55B. A cross-rib 56 that is provided in protrude-manner from the
ceiling plate 14A of the case 12 is inserted into the rotation
restriction portion 55A and relative rotation of the brake member 55 with
respect to the case 12 is restricted. The braking gear portion 55B
extends to the radial direction outer side from the lower end of the
rotation restriction portion 55A and is engageable with the engaging gear
44 of the reel 11.

[0047] The brake member 55 is constituted to be capable of selectively
assuming a braked position and a rotation-allowed position by displacing
in the axial direction of the reel 11 inside the case 12 when not in use.
At the braked position, the braking gear portion 55B is meshed with the
engaging gear 44. At the rotation-allowed position, the meshing between
the braking gear portion 55B and the engaging gear 44 is released. The
compression coil spring 58 is disposed in a compressed state between the
ceiling plate 14A of the case 12 and the brake member 55. The brake
member 55 is displaced to the braked position by the urging force of the
compression coil spring 58.

[0048] The recording tape cartridge 10 is further provided with the clutch
member 60, which is operated from the outside when a state of locking of
the reel 11 by the brake member 55 is to be released. The clutch member
60 is pushed by the rotary shaft 100 when the driving gear 102 of the
rotary shaft 100 of the drive device meshes with the reel gear 42, and
displaces the brake member 55 upward, that is, toward the
rotation-allowed position.

[0049] Specifically, the clutch member 60 is disposed between the floor
portion 36 of the reel 11 and the brake member 55, and includes a clutch
main body 62 that penetrates through the floor portion 36. Respective
plural numbers of guide ribs 64 and stopper ribs 68 are provided
extending to the radial direction outer side from the clutch main body
62. The guide ribs 64 are inserted into rotation restriction slots 66
that are formed in the clutch boss portion 52 of the reel 11, and perform
a function of restricting relative rotation of the clutch member 60 with
respect to the reel 11 and a function of guiding the clutch member 60 in
the axial direction of the reel 11. The stopper ribs 68 abut against
bottom faces of stopper slots 70 that are formed in the clutch boss
portion 52, and perform a function of positioning the clutch member 60 in
the axial direction with respect to the reel 11 (which includes a
disengagement prevention function).

[0050] According to the above, as shown in FIG. 7, the brake member 55 is
a structure of which the braking gear portion 55B is meshed with the reel
gear 42 by the urging force of the compression coil spring 58 when the
recording tape cartridge 10 is not in use, and rotation of the reel 11
relative to the case 12 is prevented. However, as shown in FIG. 8, when
the reel gear 42 of the reel 11 is meshed with the driving gear 102 of
the rotary shaft 100 of the drive device, the clutch member 60 that is
pushed by the rotary shaft 100 displaces the brake member 55 to the
rotation-allowed position, and rotation of the reel 11 relative to the
case 12 is allowed.

[0051] --Detailed Structure of Reel--

[0052] As shown in FIG. 1, the reel 11 according to this exemplary
embodiment is a two-piece structure, of a hub with lower flange member 72
attached thereto and an upper flange member 74. The hub with lower flange
member 72 is integrally formed of the reel hub 32 and the lower flange
38. The upper flange member 74 is a flange member that serves as a
principal portion of the upper flange 40. The reel hub 32 and lower
flange 38 of the hub with lower flange member 72 are integrally formed by
injection-molding of a glass fiber-reinforced resin (GFRP), which serves
as a fiber-reinforced resin. This exemplary embodiment has a structure in
which the reel plate 54 made of metal is fixed in the floor portion 36 by
insert-molding.

[0053] Giving further description of the GFRP constituting the hub with
lower flange member 72, this GFRP is a resin in which approximately 10%
by weight of glass fibers serving as reinforcement fibers are mixed into
a polycarbonate that serves as a thermoplastic resin. The GFRP has, for
example, a bending elastic modulus of approximately 3400 MPa.

[0054] The upper flange member 74 is a structure in which an annular rib
76 protrudes from an inner edge portion of the upper flange 40 formed in
an annular shape. The annular rib 76 fits into an inner periphery of the
tube portion 34 of the reel hub 32. In a state in which the annular rib
76 is fitted into the upper side opening end of the tube portion 34 of
the reel hub 32, a radial direction outer side region of the annular rib
76 (a region between the upper flange 40 and the annular rib 76) is fixed
to an upper end face 34A of the tube portion 34 by ultrasonic welding or
the like. Thus, the upper flange member 74 is structured.

[0055] The upper flange member 74 is constituted by a material with a
higher bending elastic modulus than the material constituting the hub
with lower flange member 72. Specifically, the upper flange member 74 is
constituted by a GFRP with a content of 20-30% by weight of glass fibers
in the same kind of polycarbonate as the polycarbonate constituting the
hub with lower flange member 72. In this exemplary embodiment, the GFRP
constituting the hub and upper flange member 74 has a bending elastic
modulus of approximately 6600 MPa (if the glass fiber content is 30% by
weight).

[0056] The reel 11 constituted by the materials described above is
deformed relative to a state in which the magnetic tape T is not wound
thereon by a winding pressure that is applied in the state in which the
magnetic tape T is wound on. In a state after this deformation of the
recording tape cartridge 10, a space (distance) D that is a magnitude(s)
(a scalar quantity) of an edge clearance Ce that is a gap/gaps in the
width direction of the magnetic tape T (the axial direction of the reel
11) between the lower flange 38 and/or the upper flange 40, and the
magnetic tape T is prescribed. This is described more specifically below.

[0057] When the reel hub 32 provided with the tube portion 34, whose upper
side is opened as described above, is deformed by the winding pressure of
the tape, the magnetic tape T is wound round the tube portion 34 so as to
be offset to one side, for example, toward the upper flange 40 as shown
in FIG. 2. Hence, of spaces D of the edge clearance Ce, an outer
periphery side space (distance) Do, which is the shortest distance
between a lower end Tod of the outermost periphery portion of the
magnetic tape T and the lower flange 38, in the state shown in FIG. 3 in
which the magnetic tape T is completely wound on, is prescribed. In this
exemplary embodiment, the distance Do specified as described above is
given the following.

0.18 mm≦Do≦0.46 mm

If the edge clearances Ce are formed at both hub axial direction sides,
the above Do is the sum of the upper side Do and the lower side Do. Note
that taper shape of the upper and lower flanges is exaggerated in FIG. 2
and FIG. 3.

[0058] A width W of the magnetic tape T in the present exemplary
embodiment is a nominal 12.65 mm. Therefore, in the state in which the
magnetic tape T is completely wound on, a facing distance Dfo of the
outermost periphery portion in the axial direction between the lower
flange 38 and the upper flange 40, at a radial direction position
corresponding (coinciding) with the outermost periphery position of the
magnetic tape T, satisfies the following expression.

12.83 mm≦Dfo≦13.11 mm

That is, the facing distance Dfo has a dimensional tolerance of 0.14 mm
and the following expression applies.

Dfo=12.97 mm±0.14 mm

[0059] Meanwhile, in the state in which the magnetic tape T is completely
wound on, a facing distance Dfi in the axial direction between the lower
flange 38 and the upper flange 40 at a radial direction position
corresponding (coinciding) with the innermost periphery position of the
magnetic tape T (the outer periphery face of the tube portion 34),
satisfies the following expression.

12.65 mm≦Dfi≦12.77 mm

That is, the facing distance Dfi has a dimensional tolerance of 0.06 mm,
and the following expression applies.

Dfi=12.71 mm±0.06 mm

[0060] The facing distances Dfi and Dfo mentioned above are described
further. The facing distance Dfi at the innermost periphery portion is
determined as follows in consideration of the width W of the magnetic
tape T and a fabrication tolerance (surface runout) Ai (not shown in the
drawings) of each of the lower flange 38 and the upper flange 40 at the
innermost periphery portion.

Dfi=W+|Ai|×2+Ai×2

In this exemplary embodiment, the facing distance Dfi is specified as
described above given the following.

Ai=±0.03 mm

[0061] The facing spacing Dfo at the outermost periphery portion is
determined in consideration of a manufacturing tolerance Ao of each of
the lower flange 38 and the upper flange 40 at the outermost periphery
portion, the fabrication tolerance Ai of each of the lower flange 38 and
the upper flange 40 at the innermost periphery portion, and a minimum
flange taper amount Dtmin that is needed (required for both the upper and
lower flanges) in a case in which a tilt of the rotary shaft 100 of the
drive device and suchlike are taken into account.

Dfo=Dfi+|Ai|×2+Dtmin×2+|Ao|×2+Ao×2

In this exemplary embodiment, the facing distance Dfo is specified as
described above given the following.

Ao=±0.07 mm

Dtmin=0.03 mm

[0062] The space D of the edge clearance Ce is expressed, with a
difference between the facing distance Df between the upper and lower
flanges 38 and 40 and the width W of the magnetic tape T, as follows.

D=Df-W

Do=Dfo-W

Thus, in the present exemplary embodiment, the space D of the edge
clearance Ce between the upper and lower flanges 38 and 40 and the
magnetic tape T is set to a minimum space that satisfies the requirements
of fabrication (mass production) and the requirements of use (winding and
unwinding of the tape). In particular, the minimum value of the space Do
of the edge clearance Ce is specified as described above subject to the
constraints of the requirements of fabrication (mass production) and the
requirements of use.

[0063] Further description of (an example of) a practical method of
measuring the facing distances Dfi and Dfo between the upper and lower
flanges 38 and 40 is now given. Plural measurement points are specified
along the circumferential direction for the respective innermost
periphery portion and the outermost periphery portion, which points are
at the radial direction positions at the facing spacings Dfi and Dfo in
the upper and lower flanges 38 and 40. In this example, measurement
points are specified at 12 locations at 30 degree intervals at each of
the innermost periphery portion and the outermost periphery portion in
each of the upper and lower flanges 38 and 40 (a total of 48 locations).
The positions of the measurement points in the circumferential direction
coincide between the lower flange 38 and the upper flange 40.

[0064] First, in the state in which the magnetic tape T is completely
wound on, the axial direction positions of the measurement points at the
lower face of the lower flange 38, which is the face at the opposite side
thereof from the side at which the magnetic tape T is disposed, are
measured with a three-dimensional measurement instrument or the like. On
the basis of the measurement results, average heights Hi38 and
Ho38 of the measurement points at the innermost periphery portion
and the outermost periphery portion from a predetermined reference plane,
which is a plane orthogonal to the axial direction, are calculated.
Similarly, in the state in which the magnetic tape T is completely wound
on, the axial direction positions of the measurement points at the upper
face of the upper flange 40, which is the face at the opposite side
thereof from the side at which the magnetic tape T is disposed, are
measured with the three-dimensional measurement instrument or the like.
On the basis of the measurement results, average heights Hi40 and
Ho40 of the measurement points from the above mentioned reference
plane at the innermost periphery portion and the outermost periphery
portion are calculated.

[0065] Then, the magnetic tape T is unwound from the reel 11 and removed.
In this state, axial direction positions of the measurement points are
measured at both the upper and lower faces of the lower flange 38 with
the three-dimensional measurement instrument or the like. On the basis of
these measurement results, average thicknesses ti38 and to38 at
the innermost periphery portion and outermost periphery portion of the
lower flange 38 are calculated. Similarly, axial direction positions of
the measurement points are measured at both the upper and lower faces of
the upper flange 40 with the three-dimensional measurement instrument or
the like. On the basis of these measurement results, average thicknesses
ti40 and to40 at the innermost periphery portion and outermost
periphery portion of the upper flange 40 are calculated.

[0066] On the basis of the above-mentioned average heights Hi38 and
Hi40 and average thicknesses ti38 and ti40 at the
innermost periphery portion, the facing distance Dfi in the state in
which the magnetic tape T is completely wound on is calculated. Similarly
on the basis of the average heights Ho38 and Ho40 and average
thicknesses to38 and to40 at the outermost periphery portion,
the facing distance Dfo in the state in which the magnetic tape T is
completely wound on is calculated. The calculations are as follows.

Dfi=Hi40-Hi38-ti38-ti40

Dfo=Ho40-Ho38-to38-to40

[0067] The spaces D of the respective portions of the edge clearance Ce
(which is to say, the maximum space Do at the outermost periphery
portion) are not more than a width Wg of an edge guard band Tg that is
provided at the width direction end portion of the magnetic tape T.
Therefore, if the width Wg of the edge guard band Tg is 0.46 mm or more,
the following expression applies.

0.18 mm≦Do≦0.46 mm

If the width Wg of the edge guard band Tg is less than 0.46 mm, this
width Wg is the maximum limit of the space Do of the edge clearance Ce at
the outermost periphery portion. For example, if the width Wg is 0.45 mm,
the following expression applies.

0.18 mm≦Do≦0.45 mm

[0068] Giving a further description of the edge guard band Tg, information
is recorded at a data region Td of the magnetic tape T and, as shown in
FIG. 5, a servo band Ts at which a servo signal is recorded is set
adjacent to a width direction outer side of the data region Td. The edge
guard band Tg is set adjacent to the width direction outer side of the
servo band Ts. Although not shown in the drawings, the servo band Ts and
the edge guard band Tg are set at both width direction sides of the
magnetic tape T.

[0069] By specification of the above-described inner and outer facing
distances Dfi and Dfo, the distance Df between the lower flange 38 and
the upper flange 40 is given a taper shape that is wider at the outer
periphery side than at the inner periphery side. In this exemplary
embodiment, both an upper face 38U and a lower face 40L, which are the
faces of the lower flange 38 and the upper flange 40 at the respective
magnetic tape T sides thereof, are taper faces. In this exemplary
embodiment, a center value of the facing distance Dfo is wider by 0.28
mm, that is, by 0.14 mm each above and below, than a center value of the
facing distance Dfi. That is, the upper face 38U of the lower flange 38
and the lower face 40L of the upper flange 40 are taper faces with
substantial symmetry between above and below.

[0070] Further, in the recording tape cartridge 10, the upper face 38U of
the lower flange 38 and the lower face 40L of the upper flange 40 have
taper shape such that a rate of widening (increasing) of the facing
distance Df increases from the inner periphery side to the outer
periphery side. Specifically, an amount of change dDf of the facing
distance Df per unit amount of movement dr toward the radial direction
outer side of the lower flange 38 and upper flange 40, which is a rate of
widening (dDf/dr) of the facing distance Df, is larger at the outer
periphery side than at the inner periphery side, such that the faces are
convex surfaces that protrude toward the magnetic tape T are formed. In
other words, the upper face 38U of the lower flange 38 and the lower face
40L of the upper flange 40 each protrude toward the magnetic tape T side
relative to imaginary lines IL (i.e., relative to a taper shape with a
constant rate of widening) that linearly join the inner and outer edges
of each in a sectional view taken along the axial direction and the
radial direction, as illustrated in FIG. 3.

[0071] Further description is given of (an example of) a practical method
of measuring the rate of widening (dDf/dr) of the facing distance Df of
the upper and lower flanges 38 and 40. At each of the upper face 38U of
the lower flange 38 and the lower face 40L of the upper flange 40, rows
of measurement points in which plural measurement points are arranged
along the radial direction are specified. Circumferential direction
positions of the rows of measurement points may be the same at the lower
flange 38 and the upper flange 40 and may be different. The measurement
points are arranged in the measurement point row at intervals of a
predetermined distance dr (for example, 1 mm) from the innermost
periphery portion to (a vicinity of) the outermost periphery portion.
Axial direction positions of the measurement points are measured at each
of the upper face 38U of the lower flange 38 and the lower face 40L of
the upper flange 40. Differences between the axial direction positions of
measurement points that are adjacent in the radial direction (which may
be differences between heights of the adjacent measurement points from a
predetermined reference plane that is a plane orthogonal to the axial
direction) are divided by the predetermined distance dr, and the rate of
widening of the facing distance Df (dDf/dr) is calculated for respective
positions in the radial direction. The rate of widening (dDf/dr) of the
facing distance Df may be measured at plural locations in the
circumferential direction of the lower flange 38 and the upper flange 40.
The practical measurements of the rate of widening (dDf/dr) of the facing
distance Df described hereabove may be carried out with a
three-dimensional measuring instrument or the like in a state in which
the magnetic tape T has been unwound and removed from the reel 11.

[0072] A surface roughness of each of the upper face 38U of the lower
flange 38 and the lower face 40L of the upper flange 40, evaluated as a
center line average roughness Ra, is at least 0.5 μm and at most 2
μm (0.5 μm≦Ra≦2 μm). The lower flange 38 and the
upper flange 40 that are constituted of GFRP as described above have
surface roughnesses Ra of the upper face 38U and lower face 40L that
satisfy the condition 0.5 μm≦Ra≦2 μm without a
mechanical process or the like being applied after the injection molding.

[0073] Next, operation and effects of the present exemplary embodiment are
described. As shown in FIG. 7, when the recording tape cartridge 10 with
the structure described above is not in use, the brake member 55 is
disposed at the rotation-locking position by the urging force of the
compression coil spring 58, and the braking gear portion 55B is meshed
with the engaging gear 44. Therefore, rotation of the reel 11 relative to
the case 12 is blocked. At this time, the reel gear 42 of the reel 11 is
exposed through the gear aperture 20, and the clutch main body 62 of the
clutch member 60 is inserted into the penetrating hole 50 and faces the
gear aperture 20.

[0074] When the magnetic tape T is to be used, the recording tape
cartridge 10 is loaded, in the direction of arrow A, into a bucket (not
shown in the drawings) of a drive device. When the recording tape
cartridge 10 is loaded to a predetermined depth in the bucket, the bucket
descends, the rotary shaft 100 of the drive device relatively approaches
(moves upward to) the gear aperture 20 of the case 12, and the rotary
shaft 100 retains the reel 11. More specifically, the rotary shaft 100
attracts and retains the reel plate 54 with the magnet 104, without
contact between the magnets, and the driving gear 102 is meshed with the
reel gear 42.

[0075] In association with the meshing between the reel gear 42 and the
driving gear 102, that is, with the relative movement of the driving gear
102 to approach the case 12 in the axial direction, an axial central
portion of the rotary shaft 100 abuts against the clutch main body 62 of
the clutch member 60 and pushes the clutch member 60 upward in opposition
to the urging force of the compression coil spring 58. Consequently, the
brake member 55 abutting against the clutch member 60 also moves upward,
and the meshing between the braking gear portion 55B of the brake member
55 and the engaging gear 44 is released.

[0076] Thus, the brake member 55 reaches a relative rotation-allowed
position with respect to the reel 11. When the rotary shaft 100 is moved
further upward, the clutch member 60 and the brake member 55 are lifted
upward together in the reel 11 in opposition to the urging force of the
compression coil spring 58 (without the relative positions of the clutch
member 60 and the brake member 55 changing). Thus, in the recording tape
cartridge 10, the brake member 55 reaches an absolute rotation-allowed
position (with respect to the case 12), and the lower flange 38 is
separated from the annular rib 22. As described above and shown in FIG.
8, the reel 11 floats freely inside the case 12, and is rotatable in a
state of not touching the inner faces of the case 12. Although not
described in detail here, the recording tape cartridge 10 is positioned
in horizontal directions and a vertical direction with respect to the
drive device by the bucket by the recording tape cartridge 10 descending
in the drive device.

[0077] Hence, drawing pins (not shown in the drawings) of the drawing
portion of the drive device are engaged with the leader block 30, and the
drawing portion disengages the leader block 30 from the case 12 and
guides the leader block 30 to the take-up reel of the drive device. Then,
the leader block 30 is fitted into the take-up reel and structures a
portion of a winding surface onto which the magnetic tape T is to be
wound. In this state, the leader block 30 turns integrally with the
take-up reel, and the magnetic tape T is taken up onto a reel hub of the
take-up reel while being drawn out from the case 12 through the opening
18.

[0078] At this time, the reel 11 of the recording tape cartridge 10 is
turned synchronously with the take-up reel by rotary force of the rotary
shaft 100 that is transmitted by the driving gear 102 meshed with the
reel gear 42. Information is recorded onto the magnetic tape T and/or
information recorded on the magnetic tape T is replayed by a
recording/replay head that is disposed along a predetermined tape path in
the drive device. During this, the brake member 55 that is not rotatable
with respect to the case 12 is in sliding contact with the clutch member
60 that turns, together with the reel 11, relative to the case 12.

[0079] Hence, when the magnetic tape T has been wound back to the reel 11
and the leader block 30 retained in the vicinity of the opening 18 of the
case 12, the bucket in which the recording tape cartridge 10 is loaded
ascends. Correspondingly, the meshing between the reel gear 42 and the
driving gear 102 is released, the abutting between the rotary shaft 100
and the clutch member 60 is released, and the clutch member 60 is moved
downward together with the brake member 55 (maintaining the state of
abutting against the brake member 55) by the urging force of the
compression coil spring 58.

[0080] Accordingly, the stopper ribs 68 of the clutch member 60 abut
against bottom faces of the stopper slots 70 and the braking gear portion
55B of the brake member 55 meshes with the engaging gear 44. That is, the
brake member 55 returns to the rotation-locking position that blocks
rotation of the reel 11 with respect to the case 12. In accordance with
the operation in which the brake member 55 and the clutch member 60 are
moved by the urging force of the compression coil spring 58, the reel 11
also moves downward, and returns to the initial state in which the lower
flange 38 is abutted against the annular rib 22 and the reel gear 42 is
exposed through the gear aperture 20. In this condition, the recording
tape cartridge 10 is ejected from the bucket.

[0081] Now, at the reel 11 that is being driven to rotate by the driving
gear 102 meshed with the reel gear 42 as described above, a portion of
the torque is converted to a force in the axial direction (a thrust
force) by the meshing faces 42E and 102E that are inclined with respect
to the axial direction. That is, in the reel 11, the urging force of the
compression coil spring 58 acts towards the rotary shaft 100 and the
thrust force associated with the torque transmission acts in opposition
to the urging force, so the reel rotates while fluctuating (vibrating) in
the axial direction.

[0082] As a result, the magnetic tape T runs while fluctuating in the
width direction. Of these fluctuations of the magnetic tape T, the head
of the drive device tracks (corrects position for) fluctuations which are
at a predetermined frequency or above on the basis of servo signals in
the servo band Ts. In consequence, the fluctuations have no influence on
recording and replaying of information. However, of the fluctuations of
the magnetic tape T in the width direction, components that cannot be
tracked are treated as position error signals (PES), and it is desirable
for the position error signals (amplitudes of fluctuations (vibrations)
that the head cannot follow) to be small. Conventionally, it has been
considered that PES becomes deterioration by contact between the flanges
and the magnetic tape T, so dealing with PES by widening the space D of
the edge clearance Ce.

[0083] However, the present inventors have attained new knowledge that the
smaller an edge clearance, the more position error signals (PES) are
suppressed. This point is described with reference to FIG. 6, which
illustrates position error signal (PES) measurement results. FIG. 6 shows
results in which position error signals are measured using two kinds of
test reel, TR1 and TR2, which are not included in the present invention.
The horizontal axis shows the distance between a pair of upper and lower
flanges (the distance in a state in which a magnetic tape T is not wound
thereon), and the vertical axis shows measured values of position error
signals (PES).

[0084] Test reel TR1, in the state in which the magnetic tape T is not
wound on, gives the following results.

Dfi=12.985 mm,Dfo=13.318 mm

Test reel TR2, in the state in which the magnetic tape T is not wound on,
gives the following results.

Dfi=12.783 mm,Dfo=13.081 mm

The opposing faces of the upper and lower flanges of the test reels TR1
and TR2 form taper shapes with the facing distances therebetween having
constant rates of widening. Except for the dimensions and shapes of the
upper and lower flanges described above, the test reels TR1 and TR2 have
structures the same as the reel 11.

[0085] Accordingly, FIG. 6 shows measured values of position error signals
(PES) of test reel TR2 for facing distances Df between the upper and
lower flanges in the range from 12.783 to 13.081 mm, and shows measured
values of position error signals (PES) of test reel TR1 for facing
distances Df between the upper and lower flanges in the range from 12.985
to 13.138 mm. More specifically, the position error signals (PES) are
shown for when a part of the magnetic tape T that has been wound in a
region with the corresponding facing distance Df is passing a PES
measurement sensor (in the vicinity of a head).

[0086] From FIG. 6, it can be seen that the position error signals (PES)
of test reel TR2, in which the facing distances Df between the upper and
lower flanges are relatively small, are kept smaller than the position
error signals (PES) of test reel TR1. With both the test reels TR1 and
TR2, it can be seen that the position error signals (PES) are suppressed
more at the inner periphery side at which the facing distances Df between
the upper and lower flanges are relatively small than at the outer
periphery side. The finding described above is not disclosed anywhere in
JP-A Nos. 11-306714, 2005-302256 and 2009-211743 or Japanese Patent No.
4,679,733. Giving a further description of Japanese Patent No. 4,679,733,
in the structure thereof, position error signals (PES) are reduced by a
distance between collar portions of reel being prescribed and a running
magnetic tape being reliably aligned with flanges of a guide roller at a
drive side. In contrast, according to the knowledge attained by the
present inventors, regardless of whether there are flanges at a guide
roller at a drive device or such flanges are absent, the position error
signals (PES) are kept smaller where the facing distance Df is relatively
smaller, as shown in FIG. 6. This has been experimentally verified.

[0087] In the recording tape cartridge 10, as described above, the spaces
D of the edge clearance Ce are set to values that are (close to) minimums
required for fabrication and for use. Therefore, in the recording tape
cartridge 10, position error signals (PES) that arise with running of the
magnetic tape T (rotation of the reel 11) are kept small.

[0088] In addition, in the recording tape cartridge 10, the upper face 38U
of the lower flange 38 and the lower face 40L of the upper flange 40 have
taper shape in which the rate of widening of the facing distance Df
increases from the inner periphery side to the outer periphery side, and
the upper face 38U and lower face 40L protrude toward the magnetic tape T
side relative to the imaginary lines IL. Due to this characteristic
structure, the facing distances D of the edge clearances Ce between the
upper face 38U of the lower flange 38 and the lower face 40L of the upper
flange 40, and the magnetic tape T can be made smaller than in a
comparative example provided with a pair of flanges with taper shapes
along the imaginary lines IL, that have a constant rate of widening. That
is, even in a structure in which the lower limit of the space Do at the
outermost periphery portion is constrained or restricted by the
requirements of fabrication (mass production) and the requirements of use
(winding and unwinding of the tape), a portion in which the spaces D of
the edge clearance Ce are small is expanded at the outer periphery side
region.

[0089] Thus, in the recording tape cartridge 10, the spaces D of the edge
clearance Ce are small and the position error signals (PES) are kept
small through a wide range in the radial direction. In addition, average
values of the position error signals (PES) over the whole length of the
magnetic tape T are kept small, which contributes to an improvement in
reliability of the recording tape cartridge 10.

[0090] In particular, at a portion of the magnetic tape T that is wound
relatively to the inner periphery side, the facing distance Df between
the upper and lower flanges is wider than in the state in which the
magnetic tape T is completely wound on, due to a reduction in winding
pressure associated with the magnetic tape T unwinding from the reel 11,
therefore, the spaces D of the edge clearance Ce increase during actual
running. At this time, because the upper face 38U of the lower flange 38
and the lower face 40L of the upper flange 40 have the shapes described
above, the spaces D of the image clearance Ce are small even after the
facing distances Df between the upper and lower flanges have widened, and
position error signals (PES) are kept small.

[0091] Thus, with the recording tape cartridge 10 according to the present
exemplary embodiment, position error signals (PES) can be kept small
during actual running of the magnetic tape T.

[0092] In the recording tape cartridge 10, the surface roughnesses of the
upper face 38U of the lower flange 38 and the lower face 40L of the upper
flange 40 are set to 0.5 μm≦Ra≦2 μm. Consequently,
position error signals (PES) during running of the magnetic tape T can be
kept even smaller. That is, in the structure in which the spaces D of the
edge clearance Ce are small, the magnetic tape T runs while touching
(sliding) against the upper face 38U of the lower flange 38 and/or the
lower face 40L of the upper flange 40. Due to that the surface roughness
described above is set to be more than or equal to 0.5 μm, friction
between the magnetic tape T and the upper and lower flanges 38 and 40 can
be reduced, and position error signals (PES) of the magnetic tape T can
be reduced. Meanwhile, due to that the surface roughness is set to be
less than or equal to 2.0 μm, a deterioration in position error
signals (PES) due to surface roughness (protrusions and indentations) of
the upper face 38U and lower face 40L can be suppressed.

[0093] Because the hub with lower flange member 72 and the upper flange
member 74 of the reel 11 are constituted of GFRP, which is a
high-elasticity material, deformations of the reel hub 32, the lower
flange 38 and the upper flange 40 themselves due to winding pressure of
the magnetic tape T are suppressed. Therefore, the outer periphery side
space Do, and Dfo and Dfi can be accurately obtained in the state in
which the magnetic tape T is completely wound on, which contributes to
keeping position error signals (PES) small as described above.

[0094] In particular, with the reel hub 32 in which the floor portion 36
is provided at one end of the tube portion 34 and the other end of the
tube portion 34 is an opening end, stiffness at the opening end side
tends to be insufficient relative to the stiffness at the floor portion
36 side. However, the upper flange 40 that is constituted of a material
with a higher elasticity than the material constituting the reel hub 32
is fixed to the opening end of the tube portion 34. Therefore, the
opening end side of the tube portion 34 is reinforced by the upper flange
40, and deformations of the reel hub 32, the lower flange 38 and the
upper flange 40 themselves are even more effectively suppressed.
Moreover, differences in degrees of deformation between the two axial
direction sides are small. Therefore, a shape in which the magnetic tape
T is wound on the tube portion 34 is stable, which contributes to
position error signals (PES) being kept even smaller.

[0095] In the recording tape cartridge 10 described above, the spaces D of
the edge clearance Ce are not more than the width Wg of the edge guard
band Tg of the magnetic tape T. Therefore, if there is a single
protruding wind Tz of the magnetic tape T as illustrated in FIG. 2, due
to irregular winding of the magnetic tape T or the like, folding of the
servo band Ts of the magnetic tape T is prevented or effectively
suppressed. That is, if a circumferential portion of the protruding wind
Tz makes contact with the lower flange 38 due to transportation of the
recording tape cartridge 10 or a fall or the like, folding occurs at the
protruding wind Tz. However, because the spaces D of the edge clearance
Ce are not more than the width Wg of the edge guard band Tg of the
magnetic tape T, the protruding wind Tz is kept within the range of the
edge guard band Tg, and a portion at which folding occurs is within the
range of the edge guard band Tg. Therefore, occurrences of servo errors,
which are failures in reading of the servo signal by the head of a drive
device, are suppressed.

[0096] In particular, in the recording tape cartridge 10, the upper face
38U of the lower flange 38 and the lower face 40L of the upper flange 40
have the taper shape with the faces protruding toward the magnetic tape T
side relative to the imaginary lines IL as described above. Thus, a range
in which the spaces D of the edge clearance Ce are sufficiently smaller
than the width Wg of the edge guard band Tg is set to be wide in the
radial direction of the reel 11. Therefore, even if folding occurs at the
edge guard band Tg, the folding occurs at a region that is separated in
the width direction of the magnetic tape T from the servo band Ts.
Therefore, folding of the edge guard band Tg is less likely to affect
states of contact of the servo band Ts with the head, and occurrences of
servo errors are even more effectively suppressed.

[0097] Herein, in the exemplary embodiment described above, an example is
presented in which the upper flange member 74 is joined to the hub with
lower flange member 72 in which the lower flange 38 is formed integrally
with the reel hub 32 (which is referred to as a two-piece structure).
However, the present invention is not limited thus. For example, a
structure is possible in which the upper flange 40 is formed integrally
at the opening end side of the reel hub 32 and the lower flange 38 is a
separate member that is joined to the other end side of the reel hub 32.
As a further example, a structure is possible in which (a member
including) the upper flange member 74 and (a member including) the lower
flange 38 are joined to the reel hub 32 having shape of a tube with a
bottom (which is referred to as a three-piece structure).

[0098] In the exemplary embodiment described above, an example is
presented in which a polycarbonate containing glass fibers is used as the
material constituting the reel hub 32, the lower flange 38 and the upper
flange 40, but the present invention is not limited thus. It will be
clear that various materials may be used, such as, for example,
carbon-fiber reinforced resins (CFRP) and the like.

[0099] In the exemplary embodiment described above, an example is
illustrated in which the upper flange member 74 is constituted of a
material with a higher elasticity than the hub with lower flange member
72, but the present invention is not limited thus. For example, the upper
flange member 74 may be constituted of a material with the same elastic
modulus as the hub with lower flange member 72. As a further example, the
upper flange member 74 may be constituted of a material with a lower
elasticity than the hub with lower flange member 72. In such a case, a
structure in which, for example, the opening end side of the tube portion
34 is reinforced with a reinforcing member such as a metal ring or the
like is preferable.

[0100] In the exemplary embodiment described above, an example is
presented in which the reel gear 42 includes the meshing faces 42E that
are inclined with respect to the axial direction, and the axial direction
position of the reel 11 with respect to the drive device is set by the
meshing between the reel gear 42 and the driving gear 102. However, the
present invention is not limited thus. For example, a structure is
possible in which the reel 11 includes a reference portion, at a region
other than the reel gear 42, that makes contact with a positioning
portion of the rotary shaft 100 and serves as an axial direction position
reference with respect to the drive device.

[0101] In the exemplary embodiment described above, an example is
presented in which the space D of the edge clearance Ce is not more than
the width Wg of the edge guard band Tg, but the present invention is not
limited thus. For example, a structure is possible in which the space D
of the edge clearance Ce exceeds the width Wg of the edge guard band Tg.
Furthermore, the present invention is not limited to structures in which
the edge guard band Tg is set at both width direction sides of the
magnetic tape T. For example, a structure is possible in which the edge
guard band Tg is not set at a side to which the magnetic tape T tends to
be offset in the wound state.

[0102] In the exemplary embodiment described above, an example is
presented in which the upper face 38U of the lower flange 38 and the
lower face 40L of the upper flange 40 are formed with symmetry between
above and below, but the present invention is not limited thus. For
example, a structure is possible in which the upper face 38U of the lower
flange 38 and the lower face 40L of the upper flange 40 have
non-symmetrical shapes. In such a case, one of the upper face 38U of the
lower flange 38 or the lower face 40L of the upper flange 40 may be
shaped along a plane that is orthogonal with respect to the axial
direction (a shape without a taper). Alternatively, one of the upper face
38U of the lower flange 38 and the lower face 40L of the upper flange 40
may have a taper shape that linearly joins the inner and outer edges in a
sectional view taken along the radial direction and the axial direction
(a taper shape with a constant taper rate).

[0103] The upper and lower flanges of the present invention are not
limited to structures in which the rate of widening of the facing
distance Df therebetween increases continuously from the innermost
periphery side to the outermost periphery side. For example, one or both
of the upper face 38U of the lower flange 38 and the lower face 40L of
the upper flange 40 may have a structure (a composite of two conical
surfaces) in which a portion formed as a conical surface at which a rate
of widening B of the facing distance Df is constant is disposed at the
radial direction outer side of a portion formed as a conical surface at
which a rate of widening A of the facing distance Df is constant, and
B>A. Further, one or both of the upper face 38U of the lower flange 38
and the lower face 40L of the upper flange 40 may have a structure that
is a composite conical surface formed of three or more conical surfaces.

[0104] It will be clear that the present invention may be embodied with
numerous other modifications within a technical scope not departing from
the spirit of the invention.